This invention relates to passive apparatus for thermally controlling the environment of a portable device.
One embodiment of the invention involves a portable light box containing a battery and a high intensity lamp connected thereto which generates heat. Such a portable light box is used in the medical arts to provide light via a fiber bundle to endoscopic devices, such as a rhinolaryngoscope or the like, and surgical headbands of the type worn by physicians during various types of medical procedures. The light box is typically carried by the user in a pocket of a laboratory jacket or clipped to the user's belt. With constant usage, the light box can become overly warm, and thus uncomfortable when carried close to the body.
Battery operated equipment, such as the light box noted above, may also be exposed to changing outdoor conditions. Temperature extremes of both hot and cold can considerably shorten the useful life of the battery. Failure of the battery, and thus the equipment powered by the battery, can pose a danger under certain field conditions.